Four children with familial hyperlysemia have been studied in this laboratory. From results thus obtained and data reported elsewhere, it can be shown that a deficiency of lysine; ketoglutarate reductase activity in these patients prevents them from converting lysine to saccharopine. Similarly, an alternate path of lysine catabolism by way of pipecolic acid has been demonstrated for them. Further studies propose to: (1) Continue serial clinical and biochemical studies on the 3 living children with familial hyperlysinemia, (2) Determine levels of lysine and lysine metabolites in brain of one child who died, (3) Determine, in vitro, capacities of liver from this chid to convert lysien to pipecolic acid, (4) Assess the capacity of infants to handle oral loads of lysine in order to evaluate the various paths available to them for lysine metabolism, (5) Establish if pipecolic acid is a normal constituent of human serum, and (6) Determine hypusine levels in liver, kidney, muscle and brain from a patient with hyperlysinemia. BIBLIOGRAPHIC REFERENCE: Woody, N. C.: Familial Hyperlysinemia (Ltr) Arch. Dis. Child. 49:974, 1974.